By adding some functions to memories, highly parallel computation may be realized. We have proposed memory-based parallel computation models, which uses a new functional memory as a SIMD type parallel computation engine. In this paper, we consider models with communication between the words of the functional memory. The memory-based parallel computation model consists of a random access machine and a functional memory. On the functional memory, it is possible to access multiple words in parallel according to the partial match with their memory addresses. The cube-FRAM model, which we propose in this paper, has a hypercube network on the functional memory. We prove that PSPACE is accelerated to polynomial time on the model. We think that the operations on each word of the functional memory are, in a sense, the essential ones for SIMD type parallel computation to realize the computational power.

There have been several studies related to a reduction of the amount of computational resources used by Turing machines. As consequences, Linear speed-up theorem", tape compression theorem" and reversal reduction theorem" have been obtained. In this paper, we discuss a leaf reduction theorem on alternating Turing machines. Recently, the result that one can reduce the number of leaves by a constant factor without increasing the space complexity was shown for space- and leaf-bounded alternating Turing machines. We show that for time- and leaf-bounded alternating Turing machines, the number of leaves can be reduced by a constant factor without increasing time used by the machine. Therefore, our result says that a constant factor on the leaf complexity does not affect the power of time- and leaf-bounded alternating Turing machines.

A fast Viterbi decoding technique with path reduction in optical channels is presented. This decoding exploits the asymmetric characteristic of optical channels. In the decoding trellis, the branches with low or no possibility being correct path are eliminated based on the detected signal level. The number of Add-Compare-Select (ACS) operations which occupy the dominant part of Viterbi decoding is considerably reduced due to branch eliminations, and fast decoding is realized by decoding asynchronously to received sequence. The reduction of the number of ACS operations is derived for the codes with rate 1/2. It is shown that the number of ACS operations is considerably reduced compared with the conventional Viterbi decoding. The bit error probability of the proposed decoding is derived for noiseless photon counting channel. It is also shown that the decoding technique can be applied to the cases using avalanche photo diode (APD) based receiver with dark current noise at a cost of negligible degradation on the bit error probability.

We review the role of optics in interconnects, analog processing, neural networks, and digital computing. The properties of low interference, massively parallel interconnections, and very high data rates promise extremely high performance for optical information processing systems.

In this paper we review the recent progress and basic technology of vertical cavity surface emitting lasers together with related parallel surface operating optical devices. First, the concept of surface emitting lasers is presented, and then currently developed device technologies will be reviewed. We will feature several technical issues, such as multi-layer structures, 2-dimensional arrays, photonic integration, etc. Lastly, future prospects for parallel lightwave systems will be discussed.

The heterointerfaces of Al0.3Ga0.7As/GaAs single quantum wells (SQWs) and the characteristics of SQW lasers grown on Si substrates with Al0.5Ga0.5As/Al0.55Ga0.45P intermediate layers (AlGaAs/AlGaP ILs) entirely by metalorganic chemical vapor deposition (MOCVD) are reported. The effects of thermal cycle annealing on the crystallinity and the lasing characteristics of GaAs/Si are also reported. By using the AlGaAs/AlGaP ILs, SQWs with a specular surface morphology and a smoother heterointerface can be grown on a Si substrate. Thermal cycle annealing is found to improve the crystallinity of GaAs/Si and to contribute to room-temperature continuous-wave operation of lasers on Si substrates. The combinations of the techniques of AlGaAs/AlGaP ILs and thermal cycle annealing improve the lasing characteristics: an average threshold current density of 1.83 kA/cm2, an average differential quantum efficiency of 52%, an internal quantum efficiency of 83%, an intrinsic mode loss coefficient of 23 cm-1, a differential gain coefficient of 1.9 cm/A, and a transparency current density of 266 A/cm2, which are superior to those of the two-step-grown laser on a Si substrate. The improvements of the lasing characteristics result from the smooth heterointerfaces of the AlGaAs/AlGaP ILs.

We propose Polarization-Shift-Keying (POLSK) homodyne system using phase-diversity receivers and theoretically analyze its bit-error-rate (BER) performance. Since the proposed system uses polarization modulation and homodyne detection, it can cancel the phase noise and is attractive at a high bit-rate transmission. It is found that the receiver sensitivity of the proposed POLSK homodyne system is the same as that of POLSK heterodyne system and is much better than that of DPSK phase-diversity homodyne systems at high signal-to-noise ratio (SNR). We also cosider theoreically the effect of the fluctuation of state of polarization (SOP) on the BER performance of POLSK homodyne system.

We propose parallel rate-variable punctured convolutional coded PPM in photon communication to achieve high energy information efficiency Ie for desired bit error rate (BER) and transmission bandwidth. We theoretically show the BER performance, bandwidth expansion factor β and necessary Ie to achieve BER10-6 of the proposed systems for some combinations of code rates. It is found that the proposed system can achieve high Ie for desired BER and β by selecting a suitable combination of code rates depending on the channel conditions. Moreover, it is showm that the proposed system has better BER performance than RS-coded PPM in the range of small β.

A new MOS linear operational transconductance amplifier (OTA) for the up-to-4 MHz range OTA-C filters is proposed. The proposed OTA is designed using a new linearizing technique based on bias-current modulation, to compensate nonlinearities in the transfer characteristic of the conventional current-source-biased source-coupled pair. The design and SPICE simulation are presented in detail, assuming the implementation by the typical p-well CMOS process. The simulation of a 3.58 MHz OTA-C band-pass filter built with the proposed OTAs showed close agreement with the desired performance.

In this letter we study the wave propagation in a diode-equipped microstrip line and show that soliton generation at microwave frequencies is possible with monolithic fabrications of such nonlinear transmission lines. We propose that this phenomenon be utilized as a new method of obtaining ultrashort electrical pulses with picosecond durations. The perdicted soliton generation has been confirmed by computer simulations based on the harmonic balance method.

This paper investigates the performance of the line spectrum pair (LSP) frequency parameter representation for speech recognition. Transitional parameters of LSP frequencies are defined using first-order regression coefficients. The transitional and the instantaneous frequency parameters are linearly combined to generate a single feature vector used for recognition. The performance of the single vector is compared with that of the cepstral coefficients (CC) representation using a minimumdistance classifier in speaker-independent isolated word recognition experiments. In the speech recognition experiments, the transitional and the instantaneous coefficients are also combined in the distance domain. Also, inverse variance weighted Euclidean measures are defined using LSP frequencies to achieve Mel-scale-like warping and the new warped-frequencies are used in recognition experiments. The performance of the single feature vector defined with transitional and instantaneous LSP frequencies is found to be the best among the measures used in the experiments.

The heterointerfaces of Al0.3Ga0.7As/GaAs single quantum wells (SQWs) and the characteristics of SQW lasers grown on Si substrates with Al0.5Ga0.5As/Al0.55Ga0.45P intermediate layers (AlGaAs/AlGaP ILs) entirely by metalorganic chemical vapor deposition (MOCVD) are reported. The effects of thermal cycle annealing on the crystallinity and the lasing characteristics of GaAs/Si are also reported. By using the AlGaAs/AlGaP ILs, SQWs with a specular surface morphology and a smoother heterointerface can be grown on a Si substrate. Thermal cycle annealing is found to improve the crystallinity of GaAs/Si and to contribute to room-temperature continuous-wave operation of lasers on Si substrates. The combinations of the techniques of AlGaAs/AlGaP ILs and thermal cycle annealing improve the lasing characteristics: an average threshold current density of 1.83 kA/cm2, an average differential quantum efficiency of 52%, an internal quantum efficiency of 83%, an intrinsic mode loss coefficient of 23cm-1, a differential gain coefficient of 1.9cm/A, and a transparency current density of 266 A/cm2, which are superior to those of the two-step-grown laser on a Si substrate. The improvements of the lasing characteristics result from the smooth heterointerfaces of the AlGaAs/AlGaP ILs.

This article briefly looks at the future of telecommunication education in the universities as it evolves from present concerns and trends. Five year bachelor's programs and top-down curricular design will be common. Textbooks supplemented by advance organizers, instruction and testing according to individual learning styles and global integration of education using multi-media services and broadband technology will be some of the other features. Finally, the importance of industry-university partnership in all aspects of engineering education is emphasized.

We propose Polarization-Shift-Keying (POLSK) homodyne system using phase-diversity receivers and theoretically analyze its bit-error-rate (BER) performance. Since the proposed system uses polarization modulation and homodyne detection, it can cancel the phase noise and is attractive at a high bit-rate transmission. It is found that the receiver sensitivity of the proposed POLSK homodyne system is the same as that of POLSK heterodyne system and is much better than that of DPSK phase-diversity homodyne systems at high signal-to-noise ratio (SNR). We also cosider theoretically the effect of the fluctuation of state of polarization (SOP) on the BER performance of POLSK homodyne system.

This paper proposes a knowledge-based design method of a protocol of a communication network system based on the knowledge-based design methodology for computer communication systems. In the proposed method, two knowledge models, i.e., the communication network architecture model (CNAM) and the communication protocol architecture model (CPAM), are introduced and a protocol design task is modeled as a successive transformation process of these knowledge models. Giving CNAM which represents the users' requirements concerning a communication network system, the requirements specification of a protocol is derived from CNAM and represented as CPAM. Then, the detailed requirements specification of a protocol is also derived from CPAM and represented by the formal description technique (FDT-Expressions). The derivations of CPAM and FDT-Expressions are executed by the transformation rules which represent the mappings between knowledge models. Due to formally defined knowledge models and mappings, the proposed method provides a framework of a systematic support of knowledge-based protocol design. In this paper, the formal definitions of CNAM and CPAM are given, then the derivation process of FDT-Expressions of a protocol is also formalized based on these knowledge models. Furthermore, a design example is demonstrated by using LOTOS as one of the FDT-Expressions of a protocol.

This paper presents a new connected associative memory neural network. In this network, a threshold function which has two dynamical parameters is introduced. After analyzing the dynamical behaviors and giving an upper bound of the memory capacity of the conventional connected associative memory neural network, it is demonstrated that these parameters play an important role in the recalling processes of the connected neural network. An approximate method of evaluationg their optimum values is given. Further, the optimum feedback stopping time of this network is discussed. Therefore, in our network, the recalling processes are ended at the optimum feedback stopping time whether a state energy has been local minimum or not. The simulations on computer show that the dynamical behaviors of our network are greatly improved. Even though the number of learned patterns is so large as the number of neurons, the statistical properties of the dynamical behaviors of our network are that the output series of recalling processes approach to the expected patterns on their initial inputs.

This paper proposes a new construction of the minimum knowledge undeniable signature scheme which solves a problem inherent in Chaum's scheme. We formulate a new proof system, the minimum knowledge interactive bi-proof system, and a pair of languages, the common witness problem, based on the random self-reducible problem. We show that any common witness problem has the minimum knowledge interactive bi-proof system. A practical construction for undeniable signature schemes is proposed based on such a proof system. These schemes provide signature confirmation and disavowal with the same protocol (or at the same time).

We review the role of optics in interconnects, analog processing, neural networks, and digital computing. The properties of low interference, massively parallel interconnections, and very high data rates promise extremely high performance for optical information processing systems.

In this paper, some classes of arithmetic circuits are introduced that capture the computational complexity of computing the determinant of matrices with entries either indeterminates or constants from a field. An arithmetic circuit is just like a Boolean circuit, except that all AND and OR gates (with fan-in two) are replaced by gates realizing a multiplication and an addition, respectively, of two polynomials over some indeterminates with coefficients from the field, and the circuit computes a (formal multivariate) polynomial in the obvious sense. An arithmetic circuit is said to be skew if at least one of the inputs of each multiplication gate is either an indeterminate or a constant. Then it is shown that for all square matrices M of dimension q, the determinant of M can be computed by a skew arithmetic circuit of (q20) gates, and is shown that for all skew arithmetic circuits C of size q, the polynomial computed by C can be defined as the determinant of a square matrix M of dimension (q). Thus the size of skew arithmetic circuit is polynomially related to the dimension of square matrices when it is considered to represent multivariate polynomials in both arithmetic circuits and the determinant. The results are extended to some other classes of arithmetic circuits less restricted than skew ones, and by using such an extended result, a difference and a similarity are demonstrated between polynomials represented as the determinant of matrix of relatively small dimension and those polynomials computed by arithmetic formulas and arithmetic circuits of relatively small size and degree.

The VSTEP concept and its practical application in the form of an LED-type pnpn-VSTEP demonstrating low power consumption through electro-photonic operational modes are both shown. Further, with focus primarily on the new laser-mode VSTEP with high-intensity light output and narrow optical beam divergence, the design features such as threshold gain and optical absorptivity, device fabrication, and characteristics are explained. The possibility of ultimate performance based mainly on electrical to optical power conversion efficiency, important from the application viewpoint of optical interconnection, are also discussed. Also, as two examples of functional optical interconnection achieved by VSTEP, serial-to-parallel data conversion and optical self-routing switches are shown. Finally, future opto-electronic technologies to be developed for two-dimensionally integrable surface-type optical semiconductor devices, including the VSTEP, are discussed.